Magnetoelastic effects in dilute magnetic alloys

Ultrasonic studies of $\text{Cu}$Mn, $\text{Au}$Mn and $\text{Au}$Fe alloys where the concentrations of the transition metal ranges between 1 and 10% show that the longitudinal sound velocity has a marked field dependence at temperatures below the peak in the magnetic susceptibility and a negligible field dependence above it. This suggests that there may be an ordered magnetic state in these alloys.     

Skew scattering of electrons in a spin glass

The field and temperature dependences of the extraordinary Hall effect in alloys of the $\text{Au}$Fe system have been measured for the first time over a range that encompasses the spin glass regime. We are able to show how the data reflect the competition between the spin glass ordering interactions and the disruptive effects of temperature and applied magnetic field.     

Atomic short-range order and its relation to the magnetic behavior of noble-metal based spin-glass alloys

We have investigated the spatial distribution of magnetic atoms (Mn or Fe) by determining the short range order parameters for the archetypal spin-glass alloys: $\text{Cu}$Mn, $\text{Au}$Mn, $\text{Au}$Fe and $\text{Pt}$Mn in the dilute limit. All four systems possess atomic short-range order (ASRO) such as to enhance local ferromagnetic regions. In the latter three systems the ASRO is relatively strong and initiates long-range structures which develop with increasing concentration and which eventually destroy the spin-glass state.     

II. XPS study of 3d-metal ions dissolved in noble metals

Valence and core level spectra ofAgMn,AuFe,AuCo,AuNi,CuFe,CuCo andCuNi will be reported. Clearly defined virtual bound states (vbs) can only be detected in the spin fluctuating systemsAuNi andCuNi. An increase in the density of states near the Fermi energy, in the region of the flats-p band of the host metal is observed in the other magnetic alloys. There are indications that a large hybridization between the impurity and the host metald-electrons exist. The impurity core levels show satellites. They can originate from the emission from real isolated impurities and from many body effects.     

The longitudinal magnetophonon effect in semiconductors containing magnetic impurities

The dependence of longitudinal magnetoresistance on magnetic field in semiconductors containing magnetic impurities is investigated theoretically. The calculation takes into account the scattering of electrons on magnetic impurities and on optical phonons. The inelastic optical phonon scattering itself is responsible for magnetophonon oscillations of the magnetoresistance, the extremes of these oscillations occuring when energy distance between Landau levels is equal to the energy of optical phonon, $\text{h}\text{?}$ω₀. The scattering on magnetic impurities may lead to spin flip electronic transitions. The spin flip electronic transitions manifest themselves as additional minima on the oscillatory picture of magnetoresistance. These new minima occur when the energy separation between spin-split Landau levels is equal to $\text{h}\text{?}$ω₀.     

Thermopower of concentrated AuCr alloys

Measurements are presented of the thermopower of three concentrated $\text{Au}$Cr (0.9, 4.9 and 10.6 at.%Cr) alloys between 4 and 500°K. Considerable differences are observed in the thermopower compared with $\text{Au}$Fe alloys in a similar concentration range. Possible reasons for these differences are discussed in terms of current ideas on spin glasses and the pair model of Matho and Béal-Monod.     

Analysis of the high-temperature spin-glass susceptibility: Determination of the local magnetic exchange

New measurements are reported of the magnetic susceptibility above the freezing temperature T_f for noble-metal spin-glasses with $\text{1}\text{2}$ to 6 at.% Fe or Mn. The susceptibility for T_f<T?5 T_f is not Curie-Weiss, but local magnetic correlations manifest themselves and provide a key for the determination of the exchange interactions in spin-glasses. The exchange parameters J_n are resolved up to 5 neighbors for $\text{Au}$Fe, $\text{Cu}$Mn, $\text{Au}$Mn and $\text{Pt}$Mn through a configuration ensemble calculation which includes atomic short range order.     

The susceptibility maximum in paramagnetic α-Mn and its dilute alloys

The magnetic susceptibility was measured in paramagnetic $\text{α-Mn}$, dilute $\text{α-Mn}$ V, $\text{α-Mn}$ Cr, $\text{α-Mn}$ Fe and α-Mn Co alloys. The susceptibility maximum phenomena in these alloys were found to vary systematically with impurity atoms.     

Impurity-impurity interactions in a very dilute Fe:Au system

An analysis of recent Mössbauer data of a very dilute Fe:$\text{Au}$ system strongly indicates some kind of antiferromagnetic order at low temperatures and low external fields. This shows, that even at very low impurity concentrations for this system impurity-impurity interactions are dominant. So one must be very careful in extracting from the various experimental data parameters, which characterise the Kondo behavior of the single impurities in the system Fe:$\text{Au}$.     

Spin-resolved impurity phase shifts in CuMn

Information deduced from spin-resolved scattering and exchange energy measured via the de Haas - van Alphen effect allows an examination of two recent calculations of the Mn magnetic impurity resonance in Cu. The resulting d-number N_d and spin S are in good agreement, lending further evidence for nearly integer number of d-electrons and a small $\text{long-range}$ magnetic moment. A substantial difference in majority spin density at E_F leads to an explanation for the non-observation of the Mn resonance in optical and photoemission measurements on CuMn.     

Spin relaxation rates in CuFe measured by neutron scattering

The absolute value and the temperature dependence of the spin relaxation rate of the Kondo system $\text{Cu}$Fe has been deduced from the magnetic scattering of unpolarized neutrons with energy analysis.     

Nuclear spin-lattice relaxation of dilute V,Cr and Mn in iron at very low temperatures

We report determinations of the spin-lattice relaxation rates of dilute ⁴⁸V, ⁵¹Cr and ⁵⁴Mn nuclei in polycrystalline Fe host at very low temperatures. The high-field limiting rates for $\text{FeV}$ and $\text{FeMn}$ agree well with earlier spin-echo results. The rate for $\text{Fe}$Cr fits the systematics and is in agreement with a recent ab initio calculation. A dependence of the relaxation rates on applied magnetic field was observed, similar to that seen for other impurity nuclei in Fe.     

The apparent Dingle temperature in Zn−Mn,Zn−Cr,and Zn−Fe

The apparent Dingle temperature of the 3rd zone needles in several alloys of Zn?Mn, Zn?Cr and Zn?Fe has been determined from the absolute amplitude of the de Haas-van Alphen effect over the temperature range 1.6 K to 4.2 K and the field range 0 to 9 kG. The results show clearly that potential scatteringnot spin scattering dominates in all three systems. In addition, a “cross-over” behaviour in the de Haas-van Alphen amplitudes results from the scattering of the magnetic moments of the impurity spin.     

Extrinsic spin Hall effect induced by iridium impurities in copper

We study the extrinsic spin Hall effect induced by Ir impurities in Cu by injecting a pure spin current into a CuIr wire from a lateral spin valve structure. While no spin Hall effect is observed without Ir impurity, the spin Hall resistivity of CuIr increases linearly with the impurity concentration. The spin Hall angle of CuIr, (2.1±0.6)% throughout the concentration range between 1% and 12%, is practically independent of temperature. These results represent a clear example of predominant skew scattering extrinsic contribution to the spin Hall effect in a nonmagnetic alloy.     

The impurity resistivity and resistivity minima in AlCr and AlMn alloys

The impurity resistivity of $\text{Al}$Cr between 1.5 and 50°K was determined with a characteristic temperature for the T² variation θ₁=960±40°K. The behaviour of the resistivity minimum both in $\text{Al}$Cr and $\text{Al}$Mn alloys with impurity concentration provides evidence that a T³ phonon resistivity is found also in aluminium with anomalous impurity resistivity.     

Experimental susceptibility of CuFe, AgFe and MoFe and the results of the Wilson theory

The low temperature susceptibility of the local moment system $\text{Mo}$Fe has been measured by the Mössbauer effect. The susceptibility for this system and for the system $\text{Cu}$Fe, $\text{Ag}$Fe and $\text{Au}$Fe show general agreement with the prediction of the Wilson theory.     

Skew scattering of the electrons by Ce impurities in La

Low temperature measurements of the Hall effect in lanthanum containing cerium impurities show, in addition to the ordinary Hall effect, a contribution (nearly) proportional to the magnetization of the cerium magnetic moments. We ascribe this contribution to skew scattering by the cerium impurities. The asymmetry of the scattering can result from the mixing of the conduction band and impurity wave functions for impurities having orbital magnetism.     

Susceptibility behaviour of Mn dissolved in liquid Cu—Al-alloys

Measurements of the magnetic susceptibility of liquid Mn_0.05—Cu—Al alloys up to 1700 K indicate Curie—Weiss like behaviour at the Cu-rich end and minima of the reciprocal Mn susceptibility values as a function of the temperature 1/_ξMn(T) at the A1-rich end of the series. The occurrence of 1/_ξMn(T) minima at temperatures, which are sensitively depending on the alloy composition, hints at a transition to localized magnetic moment behaviour even in the A1-based alloys at high temperatures. Both, the aspects of extremely increasing Kondo temperature and that of decreasing spin fluctuation times, allow to discuss the susceptibility behaviour uniformly for the whole alloy series. Thus, the results do not support a fundamental distinction (magnetic—nonmagnetic) between the alloy systems $\text{Cu}$—Mn and $\text{A1}$—Mn.     

Tailoring the spin density waves in Fe/Cr multilayers by selective inclusion of Sn, V and Mn

The possibility of tailoring the spin density waves in Fe/Cr(0 0 1) multilayers through the selective inclusion of Sn, V and Mn monolayers is investigated with the density functional tight-binding linear muffin-tin orbital method in the generalized gradient approximation of the exchange and correlation potential. Despite the non-magnetic character of Sn and V when substituting Cr atoms located at the nodes, the modifications induced on the spin density waves are important due to the strong hybridization. In general we find that V modifies drastically the global features of the spin density waves leading to the onset of a magnetically dead region in the Cr spacer whereas Mn inserted at the nodes rather destroys the density wave working in favor of stabilizing the layered antiferromagnetic structure. The trends obtained are consistent with experimental data when available. Since both the magnetic profile and the position of the nodes at the spacer can be modified, the present results are relevant in the context of the spin-dependent transport through magnetic multilayers in which the magnetoresistance will vary if the scattering regions across the transport direction are modified.     

High-field magnetization of PdMn and PdFeMn spin glass-ferromagnetic alloys

We have measured the low-temperature magnetization of $\text{Pd}$Mn (4.0 and 9.8 at% Mn) and $\text{Pd}$FeMn (0.35 at% Fe, 0.5 at% Mn) with fields ? 15T. A different magnetization behaviour is noted between the 9.8 at% spin glass and the alloys with lower Mn-concentrations. The latter show a ferromagnetic character and no irreversibilities or relaxation effects.